Santiago Barreira was born in Puertollano, Spain, but moved to Vila Seca at a young age, where he still lives and works. He started his artistic career in the summer of 1984 by painting and selling oil paintings, mainly landscapes. In 1986, he worked as a lay-out man with the regional Diara de Tarragona newspaper. He then worked in advertising for a while, until he joined the Comicup studios in Barcelona in 1991, where he began producing comics. For the Italian market, he has drawn for the Disney magazine Topolino, as well as an Italian-English dictionary for children.
For France, he has illustrated a comic adaptation of 'Snow White', which was published by Dargaud in the early 1990s, a 'Darkwing Duck' story for the Disney Club, and stories for Le Journal de Mickey and Picsou. His main occupation for the French Disney production is 'Les Petits Boulots de Donald', the gag strip on the back cover of Le Journal de Mickey, which he has illustrated with scripts by Gégé and Bélom since 1996. In addition, he has done artwork for 'Sjors en Sjimmie' and the Donald Duck weekly in The Netherlands. Barreira has drawn 'Duckies' gag pages in the mid-1990s, and several 'Donald Duck' and 'Junior Woodchucks' stories.